An Acoustic Device for Preventing Spine Surgery Complications A specific and immediate concern arises in spine surgery, where an inserted instrument can damage the structures around the spine. For example, a device can be advanced too far into the vertebral body, and can cause damage to the nearby spinal cord and spinal nerve roots. These complications occur despite the use of a variety of approaches that image the spine in order to ascertain instrument tip location, but require intra-operative patient exposure to ionizing radiation, usually in the form of radiographs, fluoroscopy, and computerized axial tomography scans. We propose to conduct a feasibility study to explore and develop a dynamic real- time interactive device insertion system based on quantitative ultrasound, in conjunction with A-mode and B-mode imaging, as a means by which to achieve proper guidance and positioning of the instrument. Such a system does not require any ionizing radiation. The study involves the conduct of experiments to acoustically determine the elastic properties of bone. In both cortical and cancellous bone, in vitro experiments are conducted on acoustic scattering, attenuation losses, elastic moduli, and the velocity of sound. Experiments are conducted to determine the optimal transducer characteristics that will provide satisfactory imaging results in bone. Ex vivo experiments are also performed on excised animal vertebral bodies and intact spines. Additional experiments will be performed to develop imaging criteria for distinguishing between marrow and cortex, as to what constitutes proper instrument positioning, when a complication has occurred, and how to detect the presence of imaging artifacts. PROJECT NARRATIVE The relevance of this study to public health is that the proposed acoustic device can improve the efficacy and safety of spine surgery procedures. The proposed acoustic device can guide the surgical instrument, reduce the need for ionizing radiation, and reduce complications. [unreadable] [unreadable] [unreadable]